The invention relates to a pouch or bag of a heat shrinkable gas-barrier, thermoplastic film for packaging one or a plurality of items and to a method of packaging an article in this pouch or bag.
Specifically the invention relates to an easy openable bag or pouch for vacuum shrink packaging characterized by the fact that it has two hems that can be easily gripped, facilitating the opening.
One of the packaging methods that are in common practice today is vacuum shrink packaging, according to which an article of interest is wrapped with a heat-shrinkable thermoplastic film, that is in the form of a bag, a sheet folded in two or the like and the package is vacuumised, heat sealed and cut off along the edge portions. The obtained package is heat shrunk to provide a tight appearance. The heat shrink packaging is gaining increased popularity because it adds to the aesthetic appeal of the packaged articles, thereby enhancing their commercial value and it permits easy packaging of articles even if they have complex shapes.
On the other hand, packages overwrapped in heat-shrinking film have the disadvantage that overpwraps stick so closely to the underlying surfaces and are in such tension that they are difficult to tear when the package must be torn open.
Various methods have so far been proposed with a view to overcoming this problem and facilitating the opening of packages that are made of heat shrunk films. Said methods include: i) forming a line of perforations in a specified position on a heat shrinkable film so that one can open the package by tearing it along said line; ii) making a U-shaped hole in a specified site on the film and attaching a paper seal over the hole to form a seal label that serves as an aid in opening the package; and iii) additionally attaching a so-called xe2x80x9copening tapexe2x80x9d.
However these conventional methods have their own limitations. In the first approach, the perforations will grow in size upon heat treatment of the heat shrinkable film and contaminants can potentially get into the package through the holes, thereby reducing the commercial value of the contents. In some cases, the perforations may rupture during handling. The second approach needs a special apparatus for making the U-shaped hole and, furthermore, the use of paper seals adds to the production cost. These two methods are not suited to vacuum packages. The third approach has the inherent disadvantage of being cumbersome.
One further easy opening system available for heat shrunk bags is disclosed in EP-A1-745539 where a heat shrinkable film wrap for a food product has an edge zone isolated from the remainder by a seal between opposed film layers, and a cut extending inwardly in the zone from one edge to form a tongue when heat-shrunk to facilitate opening. The film is wrapped around the product, heat sealed peripherally and then heat-shrunk. The zone is preferably separate from and adjacent to the package closure heat seal, and may be heat-sealed peripherally or over its entire area. The film may be a bag for packaging the product under vacuum, or allow packaging under a modified atmosphere.
This system has the disadvantage that, when shrunk, the protruding tongue is not visible and is difficult to grip, thus leading to an unpleasant appearance and sometimes even to an accidental break of the package. There is therefore the need for a sure easy opening system with a better packaging appearance.
The inventors have found that when in a vacuum packaging process a bag or a pouch is employed comprising a seal along a line, in-between the bottom and the mouth connecting the two side edges and defining with the closed bottom of the bag or pouch and part of the side edges a closed, airtight area, said closed bottom also comprising another seal extending from the closed bottom inward the closed, airtight area; the two hems, that are thus created, can be pulled one backward and the other forward to open the package.
The airtight area may also contain an amount of gas, typically air, such that it balloons upon heat treatment creating two pillow shaped hems having a better packaging appearance. The gas present in the airtight area may also reduce the shrinkage of the thermoplastic film in that area.